The present invention relates generally to rotary offset printing presses. More specifically, the present invention relates to a variable gap adjusting device for adjusting the gap between a metering roller and a fountain roller, and for stabilizing the metering roller during press operations.
Rotary offset printing presses typically employ a metering roller mounted closely adjacent to a fountain roller such that the rollers define a small gap between each other. A raised bearer ring on the fountain bears against the body of the metering roller in order to maintain a gap between the rollers. During operation of the press, it is desirable that the gap or distance between the rollers be precisely controlled. Ideally, a gap size of 3-5 thousandths of an inch is desirable.
However, during operation of the printing press it is quite common to experience a certain amount of ink buildup between the raised bearer ring and the metering roller. This ink build up gradually changes the gap distance, which adversely affects the printing process. The present bearer ring configuration employed to determine the gap size do not provide a mechanism for maintaining a constant gap size nor do the provide a mechanism for adjusting the size of the gap. Thus the press must be stopped periodically in order to clean the rollers so that the proper gap distance can be restored, or to adjust the gap to the desired size.
Another drawback with the present bearer ring configurations is that as the rollers wear, the gap size gradually changes, which also adversely affects performance of the printing press. Because the present configurations do not allow for the adjustment of the gap, the rollers must be periodically replaced as they wear, resulting in increased down time and increased material and labor costs. Also, during normal operations the press experiences a certain amount of vibration, which may inadvertently alter the gap between the rollers. This constant gap variation also has a detrimental effect on the performance of the printing press. None of the bearer ring configurations presently employed provide a mechanism for maintaining a constant gap size.
Accordingly, there exists a need for a device for rotary offset printing presses that will enable the gap size between the metering and fountain rollers to be controlled, that will permit the adjustment of the gap, and which will stabilize the metering roller relative to the fountain roller.
The present invention allows for the precise control and variable adjustment of the gap between the metering roller and the fountain roller, which maintains the desired gap size and which permits the roller position to be adjusted to accommodate ink build up during normal press operations. The present device also allows the gap to be adjusted to account for normal wear and tear. Fast and precise adjustment of the gap is possible and the rollers are stabilized to prevent vibration and movement, thus enhancing performance of the printer.
According to one aspect of the present invention, a gap adjusting device for a rotary press comprises a frame, a fountain roller rotatably mounted to the frame, and a stabilizing member mounted adjacent to the fountain roller. A metering roller is rotatably mounted to an eccentric member, and a gap is defined between the metering roller and the fountain roller. The eccentric member is pivotally mounted to the frame by a bearing ring having an outer race, and a portion of the outer race is positioned to contact the stabilizing member. An actuator is connected to the eccentric member for rotating the eccentric member within the bearing ring, so that upon rotation of the eccentric member the size of the gap is varied.
In further accordance with one embodiment of the invention, the eccentric member includes a mechanical stop which is positioned to abut a portion of the frame, and the mechanical stop is provided with a locking adjustment screw or bolt in order to further secure the position of the eccentric member. The actuator for shifting the eccentric member is preferably an air cylinder, although a hydraulic cylinder or other mechanical actuator may also be employed. The bearing ring is provided with a clamp for fixing the position of the bearing ring relative to the eccentric member.
The stabilizing member is preferably a hardened cam, which is mounted on a bearing concentric with the central axis of the fountain roller and which is rotatable about the central axis. The cam member abuts the outer race of the bearing ring that supports the eccentric member, and serves to stabilize the position of the metering roller relative to the fountain roller. The bearing ring that supports the stabilizing member preferably includes a flange having an elongated slot, thus permitting the position of the cam member to be changed by rotating the stabilizing member within its bearing ring. A lock nut or similar device secures the position of the cam member.
The eccentric member is pivotally mounted within a bearing ring having an outer race, so that the eccentric member pivots about a pivot point. The metering roller is rotatably mounted to the eccentric member, but the central axis of the metering roller is offset from the eccentric member pivot point, so that upon rotational movement of the eccentric member, the metering roller is moved toward or away from the fountain roller, thereby decreasing or increasing, respectively, the size of the gap between the rollers.
According to another aspect of the invention, a gap adjusting device for a rotary press includes a fountain roller rotatably mounted to a frame, and a stabilizing member mounted adjacent to the fountain roller. A metering roller is rotatably supported by an adjustment member, and a gap is formed between the metering roller and the fountain roller. The adjustment member is supported for shiftable movement relative to the frame, and an abutment member mounted to the adjustment member is positioned to contact the stabilizing member. An actuator connected to the adjustment member shifts the adjustment member, thereby moving the metering roller and the fountain roller relative to each other so that the size of the gap can be varied.
In accordance with a further embodiment of the invention, a gap adjusting device for a rotary press includes a frame, a fountain roller and a metering roller is rotatably mounted to the frame so that a gap is formed between the rollers. Adjustment means having an actuator is provided for shifting one of the rollers toward or away from the other roller, thereby decreasing or increasing, respectively, the size of the gap therebetween. Stabilizing means is provided for stabilizing the metering roller.
The aforementioned features and advantages, in addition to other features and advantages, will become readily apparent to those skilled in the art upon a reading of the following detailed description.